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AIJSTPME (2013) 6(1): 11-17
Design and Development of Electronic Fuel Injection Control System Program for
Single Cylinder Diesel Engine
SittichompooS.
Combustion Technology and Alternative Energy Centre-CTAE, College of Industrial Technology, KMUTNB,
Bangkok, Thailand
Theinnoi K.
Combustion Technology and Alternative Energy Centre-CTAE, College of Industrial Technology, KMUTNB,
Bangkok, Thailand
Sawatmongkhon B.
Combustion Technology and Alternative Energy Centre-CTAE, College of Industrial Technology, KMUTNB,
Bangkok, Thailand
Abstract
This research aimed to evaluate mainly on engine-out emission of a single cylinder diesel engine on two
conditions of fuel injection system: mechanically and electronically controlled fuel injection system. The
research engine was modified to have changeable fuel injection system. The in-house built PECU was capable
of producing 3 consecutive injection pulses. Fuel pressure was adjusted between 500 bar to 1100 bar. Engine
with electronically controlled fuel injection system produced less NOx than original engine approximately
50%. However, as the result of higher injection pressure HC and CO were increased due to fuel impingement
on combustion chamber.
Keywords: Electronically controlled fuel injection system, Common Rail fuel injection system, Single cylinder
diesel engine, Multiple injection
1 Introduction
Diesel engines usage has been highly demand strategies have been developed to improve the engine
compared to spark ignition engines in order to performance. Common Rail (CR) fuel injection
simplicity, cost and performance [1]. Conventional system is one of electronically controlled fuel
diesel engines generally employ the conventional injection system that has become the main feature for
mechanically fuel controlled injection systems. The CI engine nowadays. The system is able to provide
engine’s air to fuel ratio (A/F ratio) and fuel injection various and flexible control of injections [3,4] such
timing are not precisely controlled under operating as injection event, injection pressure, injection rate
conditions, therefore; desired engine performance, and injection number in a cycle of operation.
break specific fuel consumption (BSFC), and Electronically controlled fuel injection system has
emissions level (e.g. nitrogen oxide, particulate proven to be the major improvement of diesel engine
matter) can hardly be achieved [2]. that is able to achieve reduction in both aspects of
In additions, the growing concern regarding to the fuel consumption rate and engine-out emission [5].
global warming and the depletion of fossil fuel Operating noise from the engine is also reduced, due
resource, the demand of diesel engine has gradually to the use of high pressurised fuel atomiser and
increased due to the better fuel economy, higher sophisticated control of injections pattern. The trend
durability and wider range of renewable fuel of diesel technology has been focused on increasing
(e.g. biodiesel). The researches on fuel injection injection pressure and injection strategies, which
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achieved the higher combustion efficiency and lower 2 Experimental procedure and apparatus
emissions [5,6]. 2.1 Apparatus
CR system has been employed for multi cylinder This experimental research was carried out on a
diesel engine for passenger cars and trucks. Although YANMAR TF DI 90, four stroke single cylinder
there is no single cylinder diesel engine with naturally aspiration diesel engine which is modified
electronically controlled fuel injection system and equipped with conventional Common Rail fuel
commercialised in the market. The major advantages injection system (Figure 1, 2 and 3). The CR control
of CR system can be referred in terms of injection period and fuel pressure are controlled
improvement in the thermal efficiency and fuel using in house microcontroller based software.
economy compared to mechanism injection system Combustion chamber geometry was kept unchanged.
diesel. Also, the lower fuel economy and the The engine specifications are given in table 1. A PC
controlled emission in order to keep within the programmable electronic control unit was designed
current limits and meet forthcoming scheduled to split fuel injection into multiple injections (i.e. pre-
stringent emission standards (e.g. Euro 6, Tier 4, injection, main-injection, and post- injection) with
Low Emission Vehicle III (LEV III)). Therefore, the adjustable fuel pressure up to 2000 bar.
introduction CR system in single cylinder diesel
engine should be an interesting method. However, Table 1: Experiment engine details.
the high cost implement is the main disadvantage in
this small system. Engine Before After
There are several factors contributed in order to have specification Modification Modification
a fully controlled in fuel injection such as fuel Model YANMAR TF-DI 90
injection pressure, injection timing, dwell time, and
amount of fuel injected [7]. Fuel injection pressure is Number of 1
the main advantage of CR system as it can be cylinders
controlled independently from engine speed [8] that Cylinder-head 2 valve, Over Head Valve
results in designable injection pressure at any engine
conditions. Sophisticated control of injection Combustion system Direct Injection-DI
pressure in the rail is needed to optimise with the Bore/stroke 85 mm/87 mm
variation of pressure drop between each injection
event [9] which affects actual fuel amount injected. Displacement 3
Dwell time is a crucial parameter that has the very volume 493 cm
impact on combustion process [5]. Previous studies Compression ratio 16.6:1
showed the various length of dwell time utilised
between 0.5 – 1.8 ms [5, 7, 8, 10, 11]. The reduction Cont. Rating 5.9@ 2400rpm
of dwell time is mainly development with fuel Output (kW)
injector by having faster method of actuation. The Max. Output (kW) 6.6@ 2400rpm
approaches to 0 µs of dwell time capable of Bosch Type Electronically
producing close couple multiple injection or injection Mechanically controlled fuel
trains [3] which enable more advance combustion. Injection system Fuel injection injection
In this study, a preliminary work was to design and system system
install electronically controlled fuel injection system Engine
into single cylinder agriculture diesel engine. The Fuel pump mechanically Electrically
experiment on engine performances and engine-out mounting driven driven
emission were carried out for both conditions of
engine before and after modification.
Horiba MEXA-584L gas analysis included
measurement of CO , CO by non-dispersive infrared
2
(NDIR), O2 by magnetopneumatic method, NOX by
chemiluminescence detection (CLD) and total
unburned hydrocarbons by flame ionisation detector
(FID). H2 concentrations were measured by gas
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chromatography. For all the conditions, engine out, injection system were performed at 3 different
measurements of NOX, CO and HC were recorded. injection patterns are describe in table 2. To note that
mode 0 represented standard injection with
Electric motor High pressure conventional mechanically controlled fuel injection
fuel pump system and mode 1 through mode 9 represented CR
electronic fuel injection system.
The combustion of conventional diesel fuel injection
o
Crank system with standard injection timing at 20 bTDC
position P.E.C.U. Pressure and with CR injection system setup were examined
sensor accumulator under a constant engine speed of 1500 rpm with an
engine load of 75% of maximum engine load.
Rail Table 2: Engine Test Injection Strategies
Personal pressure Fuel Mode Inj. Pressure Inj. Pattern
Computer sensor Injector (Bar) Pilot Main Post
0 200
Figure 1: CR system diagram for modified engine 1 500
2 500
3 500
4 800
5 800
6 800
7 1100
8 1100
9 1100
Figure 2: Fuel Injection Equipment Unit
In the case of engine after modification which fuel
pump was driven by external electric motor, external
energy as pumping work must be taken in account
using equation (1). Wpump was obtained during
experiment as the product of positive area of voltage
and current from electric motor.
W1000 100% (1)
t BSFCWHHV
W
6 pump
3.610
Where
= Thermal efficiency
t
Figure 3: CR injector mounted on modified cylinder W = Brake work from engine (kW)
head BSFC = Brake Specific Fuel Consumption (g/kW.h)
HHV = High Heating Value of fuel (MJ/kg)
2.2 Procedure
The experimental were carried out on a engine test Wpump = Work required by fuel pump (W)
rig equipped with external cooling system and an in-
house built fuel consumption meter. Tests with
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Sittichompoo S. et al. / AIJSTPME (2013) 6(1): 11-17
3 Results and discussion )e 70
ko 500 bar 800 bar 1100 bar
3.1 Fuel injector test /trs60
g 50
The experiment on fuel injector at various injection n (m
patterns as shown in table 3 and injection pressure tio 40
intended to observe the in-house built control unit tra
capability to manipulate both fuel injection pressure ne 30
cn
in the pressure accumulator (rail) and injection event. co 20
Fuel amount injected was under validation with on 10
standard injector test bench Bosch model: H-S/EFEP tic
jen 0
130. Fuel injection waveform and rail pressure were I
recorded for further investigations.
Injection Strategy
Table 3: CR Injector Test Conditions Figure 4: CR Injector characteristics
Inj. Duration (ms)
Strategy Pilot Main Post Injection waveforms in figure 5 show the pattern of
instantaneous fuel pressure drop of all injection
1 0 0.1 0 strategies at injection pressure of 800 bar. During
2 0 0.5 0 double injections and triple injections, pattern of
3 0 1 0 pressure drop were uniform. They occurred at the end
of injection almost the same time at falling edge of
4 0.27 0.1 0 injection waveform. These instantaneous pressure
5 0.27 0.5 0 drop [9] were caused by the effect of fuel in pressure
6 0.27 1 0 accumulator (rail) begin to compensate the absence
of pressure during the control piston moving down to
7 0.27 0.1 0.1 close injector needle. This simultaneously happens
8 0.27 0.5 0.2 when pressure balanced valve [3] is closing. The rail
9 0.27 1 0.3 pressure is rising again as the result of pressure
balanced value fully closed as prove of the actual end
Fuel injection rate from fuel injector has non- of injection. The result demonstrates the potential to
linearity characteristic in the beginning of injection reduce dwell time between pilot- main injections and
event as shown in figure 4. It should be noted that the main-post injection down to tens of microsecond (µs)
amount of fuel injected under lowest excitation which leads to the potential for sophisticated
duration (100µs) has no significant effect for all injection strategies.
injection pressure conditions. As solenoid actuator 20 1200
requires certain amount of time to gain sufficient t) Single injection Double injection Triple injection
lo 1000 )
electromagnetic force to lift the pressure balanced (V15 r
valve in the injector [3]. However, the longer mr 800 (Ba
fo er
injection duration (500 µs) shown the linearity ev 10 600 ssu
a re
characteristic compared to the 100 µs injection n W Pilot injection Main injection Post Injection 400 l P
duration to actually start the injection. The dwell time tio 5 ue
of 1.8 ms was used for investigated fuel injection cje 200 F
nI
strategies during experiments. The higher injection 0 0
pressure and longer injecting duration resulted in 0 0.002 0.004 0.006 0.008 0.01
increasing fuel amount injected. It can be clear that Time(s)
the linear change of fuel injection amount for Figure 5: Injection waveforms against rail pressure
strategy 2 and 3 (Figure 4). at various injection strategies.
It can be noticed that the rail pressure utilised in
double consecutive injection mode was higher than
other testing mode due to the overshooting with high
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